Prototype v4 front battery box and designing other details

After redesigning the battery boxes based on a frame it was now time for another prototype. Due to the new design of the cover and the support of the frame, the fuse and it’s holder did not fit anymore. Therefore I constructed another wooden  prototype to gain a better understanding of the cable flexibility and optimal routing. At the local construction market I bought some timber of the same size of the beams and created the frame as designed.

houten frame voorbak

And a new outer skin box and it all fits very well.

modules in houten frame

That allowed me to position the contactors, shunt and fuse.

componenten in houten frame prototype

TIG welding

The outer skin will be made from 1 mm stainless steel. The frame itself will also be made from stainless steel. TIG welding could be a nice approach. Therefore I bought a budget starter TIG set and tried it.

tig elektrode slijpen

tig probeersel

Not too bad for a first TIG weld I’d say. Very nice and smooth welding process. I bought a cheap used small stainless steel welding table that had to be lowered a bit.

RVS hoek gelast

Busbar, emergency switch, heat-shrink and corrugated tube

Furthermore I did some research on other components that I need. I did a test with 3 mm copper busbar and 20×3 was very easy to bend.

busbar zetten

In the end I’ll probably be using 25×3 mm.

Futhermore I looked at several slap switches or emergency switched to turn the car off. Even though OEM’s do not have this it is obligatory in DIY conversions. Strange because you still have the clutch and ignition to intervene as well. But in the end I found a nice and compact switch.

stop schakelaar

And I ordered some orange heat shrink with glue.

oranje krimpkous met lijm

And did a test.

testje krimpkous

I’ll be using it to seal off the main HV cable and the corrugated tube just before entering a gland nut. I also orderes some orange corrugated tube.

oranje ribbelbuis

All high voltage cables (= > 60V DC or 25V AC) must be marked orange.

Battery Management System (BMS)

I also went to New Electric again to pick up the battery management system components. That allows me to include those in my designs as well.

BMS delen

I also ordered a USB to CAN-BUS adapter to be able to configure the BMS.

USB CAN BUS adapter

And started studying the BMS documentation.

Lithium Balance nBMS documentatie lezen

Most of the BMS components will be mounted in the rear battery box.

achterbox met BMS in Onshape

Chargers and wiring

I also worked in the chargers and have chosen a Victron charger for the 12V battery.

Victron 12V lader

Earlier I concluded that the high voltage chargers would best fit in the rear sides. So I started creating a supporting frame.

houten maatplank lader

I exactly fits to have some spacing between the outer panel of the car and at the same time position the charger behind the interior panel.

Lader in frame v1

I had to add some buffer/cover that allowed for ventilation. Until after the frame was almost ready I realized that I could also turn the charger around.

lader andersom

It makes creating a mount a lot easier and still there is enough room for ventilation. To I immediately started working on the new mount.

lader frame v2

Next to the chargers there will be a junction box for power distribution and connections. Each charger will have its own fuse. The space available between the covering panel is quite tight. So I’ve been searching for a box in which the fuse-holder exactly fits and can ben installed in that enclosure. To be sure I created a prototype.

prototype junction

And after that I ordered a box that should exactly fit and it does.

junction box met fuse holder

Flowtest & Arduino wiring

Finally I did some pressure and flow tests. In a Tesla the cooling of the modules is connected in parallel. Ideally I’d like to implement it that way as well. However as a result there will be more fluid connections within the enclosure. So I did a flow an pressure test to see whether the modules can also be connected in series.

Tesla modules parallel Tesla modules in serie

But in series the pressure drop is quite significant lowering the flow too much. So it will be parallel in the end. Next step is to design/find a robust distribution block and method.

To be able to conduct the flow test I worked with my Arduino pump control design again. I have now added that project to Github as ‘EV-peripherals‘ so others can use and build on it as well.

Furthermore I upgraded my circuit from a breadbord to an Arduino prototype shield. This makes the connections more robust during testing.

schakeling op shield

In the end I’d like to design and have fabricated a custom PCB to eliminate as much fragile wiring as possible.

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OldVolvo is a classic Volvo hobby blog by Lars Rengersen.

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